Dual connectivity where a user equipment can consume radio resources provided by more than one network node is known. One of the network nodes functions as a master network node and performs data plane along with control plane signalling transmitting system information, handling connectivity and performing RRC radio resource configuration signalling with the user equipment. The other network node(s) are secondary network node(s) and communicate with the user equipment in the data plane and receive the configuration information required to do this from the master network node perhaps via a backhaul link. This backhaul communication link has latency associated with it and thus, control signalling relating to data transmission such as acknowledgement messages are preferably transmitted directly by and to the secondary network node itself. Thus, an additional PUCCH physical uplink control channel may be provided to the secondary network node which allows these control messages to be sent from the user equipment directly to the secondary network node.
Where the secondary network node has several carriers supporting several cells then for a UE that it is communicating with, a particular cell may be configured to receive the PUCCH for communication with the UE. The cell configured to receive this control channel is termed a special cell. Problems may arise where the quality of signals from the special cell drop.
It would be desirable to be able to change the cell that is configured as a special cell at a secondary network node without unduly interrupting the ongoing UE communications with the secondary network node.